many-to-many

When you have a many-to-many relationship ( related_name , not through ) and you are trying to use the admin interface you are required to enter one of the relationships even though it does not have to exist for you to create the first entry. I'm creating an app that is an event organizer. Imagine we had Event and Group models, bound with many-to-many relationship. Django related_name creates another table with the indices of the two other tables. But I see no reason why this extra table has to be populated. If I work with the database through phpMyAdmin I can create a Group without

I am using JPA 2.0 and hibernate. I have a User class and a Group class as follows: public class User implements Serializable { @Id @Column(name="USER_ID") private String userId; @ManyToMany @JoinTable(name = "USER_GROUP", joinColumns = { @JoinColumn(name = "GROUP_ID") }, inverseJoinColumns = { @JoinColumn(name = "USER_ID") } ) private Set<Group> groupList; //get set methods } public class Group { @Id @Column(name="GROUP_ID") private String groupId; @ManyToMany(mappedBy="groupList") private Set<User> memberList; //get set methods } And then, I create a user and group and then assign the user

I'm having a little difficulty getting my head around relationships in Django models. Could someone explain what the difference is between a OneToOne, ManyToMany and ForeignKey? Well, there's essentially two questions here: What is the difference (in general) between one to one, many to many, and foreign key relations What are their differences specific to Django. Both of these questions are quite easily answered through a simple Google search, but as I cannot find an exact dupe of this question on SO, I'll go ahead and answer. Note that in Django, relationships should only be defined on one

I'm trying to find this query where I want to show which hosts uses which template from my Zabbix table. The only problem is that hosts and templates are registered in the same table. They are mixed in the table with for example ID 11813 being a host and 11815 being a template. Now I've found a table where the relation between these 2 is defined: hosts_templates. This table has 3 columns: a host_template id, hostid, templateid The table hosts has many columns but also containing: hostid, name where hostid contains the hosts as well as the templates. the table hosts does have a templateid

My web application has a many-to-many link between the Station and Timetable entities, and the entity that links them is called StationTimetable , which also holds data about the linkage between the two entities. When I create a new Timetable , I want to create new (and multiple) StationTimetable entries in the database to correspond to this new Timetable . So far I've managed to get the application to save just one StationTimetable entry when the user creates a new timetable. I sort of understand why this is, and I've attempted to modify it to save multiple entries however I'm now hitting a

I have the following Django model: class Icon(models.Model): name = models.CharField(max_length=200,null=False,blank=False) class Post(models.Model): icons = models.ManyToManyField(Icon) When I write the following code: post = Post() icons = [] icon_id = form.cleaned_data['icon_1'] if (icon_id): i = Icon.objects.get(id=icon_id) icons.append(i) icon_id = form.cleaned_data['icon_2'] if (icon_id): i = Icon.objects.get(id=icon_id) icons.append(i) post.icons = icons post.save() It works fine for the most part, creating a Post object and the two Icon objects. However, if the icon_id is, say, 1 in